a b s t r a c t

Objective: Direct laryngoscopy can be performed using curved or straight blades, and providers usually choose the blade they are most comfortable with. However, curved blades are anecdotally thought of as easier to use than straight blades. We seek to compare intubation success rates of paramedics using curved versus straight blades.

Methods: Design: retrospective chart review. Setting: hospital-based suburban ALS service with 20,000 annual calls. Subjects: prehospital patients with any direct laryngoscopy intubation attempt over almost 9 years. First at- tempt and Overall success rates were calculated for attempts with curved and straight blades. Differences be- tween the groups were calculated.

Results: 2299 patients were intubated by direct laryngoscopy. 1865 had attempts with a curved blade, 367 had attempts with a straight blade, and 67 had attempts with both. Baseline characteristics were similar between groups. first attempt success was 86% with a curved blade and 73% with a straight blade: a difference of 13% (95% CI: 9-17). Overall success was 96% with a curved blade and 81% with a straight blade: a difference of 15% (95% CI: 12-18). There was an average of 1.11 intubation attempts per patient with a curved blade and 1.13 at- tempts per patient with a straight blade (2% difference, 95% CI: -3-7).

Conclusions: Our study found a significant difference in intubation success rates between Laryngoscope blade types. Curved blades had higher first attempt and overall success rates when compared to straight blades. Para- medics should consider selecting a curved blade as their tool of choice to potentially improve intubation success.

(C) 2018

Introduction

Airway management is often considered the most important aspect of patient care in an emergency situation, and Endotracheal intubation is the most secure mechanism to establish a definitive airway. The Macintosh and Miller laryngoscope blades have been the mainstay of ETI for over 70 years and are the default devices of prehospital pro- viders and physicians around the world [1]. The Macintosh is a curved blade designed to fit in the vallecula and elevate the soft pallet, while the Miller is a straight blade that is positioned posterior to the epiglottis to allow for visualization of the vocal cords [2]. Both blade styles are

? Presentations: This research was presented as a poster at the National Association of EMS Physicians 2017 Annual Meeting, January 24-26, 2017 in New Orleans, LA, USA.

* Corresponding author at: Florida Atlantic University at Bethesda Health, Division of Emergency Medicine, GME Suite Lower Level B, 2815 South Seacrest Blvd, Boynton Beach, FL 33435, USA.

E-mail address: [email protected] (S.M. Alter).

found side-by-side in EMS vehicles, emergency departments, and oper- ating rooms.

Airway management is an essential skill for emergency personnel to possess, as failure to perform successful intubation can result in patient death [3,4]. Multiple intubation attempts (greater than two) lead to un- necessary tracheal trauma, edema, Oxygen desaturation, arrhythmias, cardiac arrest, and brain damage [4]. Therefore, proper training and equipment is necessary to decrease morbidity and mortality related to airway management. Literature suggests that the epiglottis is better vi- sualized with the straight style blade whereas intubation is easier with the curved style blade [3,5]. Most providers traditionally learn to use both style blades; however, they gravitate toward one or the other due to personal or institutional preference.

Upon review of the literature, we have not identified any prehospital studies of intubation success when considering blade type. Therefore, the aim of this study is to compare intubation success with a Macintosh blade versus a Miller blade as performed during pre-hospital ETI by paramedics.

https://doi.org/10.1016/j.ajem.2018.01.100

0735-6757/(C) 2018

1808 S.M. Alter et al. / American Journal of Emergency Medicine 36 (2018) 1807–1809

Methods

Study design

This retrospective chart review of prehospital medical records was approved by our institutional review board.

Setting and population

The study was conducted at a hospital-based suburban EMS service with approximately 20,000 calls per year. All EMS vehicles were operat- ing at the advanced life support level, staffed with two paramedics, in a two-tiered EMS system. Patients who underwent direct laryngoscopy in the prehospital setting between September 2007 and July 2016 were se- lected for inclusion.

Protocol

Decision to intubate patients was at the discretion of the treating paramedics. Immediately after each patient encounter, paramedics doc- umented the intubation procedure, type of blade(s) used, number of at- tempts at intubation, and if the intubation was successful. Laryngoscope blade was selected from a dropdown box with options of curved or straight.

Measurements and analytical methods

Intubation attempt was defined as passing the blade between the central incisors. Success was defined as being able to oxygenate and ventilate the patient after intubation. Data was extracted from the prehospital medical record database. Patients missing laryngoscope blade data were excluded from the study. Aggregate first attempt ETI success rate and overall success rate were calculated using total number of attempts for all patients with curved and straight blades. Differences between the two groups were calculated with a 95% confidence interval. Average number of intubation attempts per patient was also calculated with a 95% confidence interval for both curved and straight blade attempts.

Results

During the study 2299 patients were intubated in the prehospital setting using direct laryngoscopy. Of these, 1865 had attempts with a curved blade, 367 had attempts with a straight blade, and 67 had at- tempts with both (Table 1). Baseline characteristics of age, weight, and gender were similar between both groups (Table 1).

There were a total of 2150 intubation attempts with curved blades on 1932 patients, an average of 1.11 intubation attempts per patient. There were a total of 491 intubation attempts with straight blades on 434 patients, an average of 1.13 attempts per patient. There was a 2% difference in intubation attempts between curved and straight blades (95% CI: -3-7) (Table 2).

Paramedics successfully intubated 1659 patients on the first attempt using a curved blade (86%) and 317 patients on the first attempt using a straight blade (73%). This is a difference of 13% (95% CI: 9-17). Overall paramedics successfully intubated 1822 patients with a curved blade

Table 1

Baseline characteristics.

Curved Straight

n^a 1865 367

^a 67 patients had attempts with both curved and straight blades.

Table 2

Success rates and intubation attempts for curved and straight blade laryngoscopes.

(96%) and 351 patients with a straight blade (81%). This is a difference of 15% (95% CI: 12-18) (Table 2).

Discussion

Patients requiring ETI are often critically ill and should have defini- tive airways placed without fail. In physician- and non-physician- provided prehospital care, ETI first-attempt Failure rates have been re- ported to range between 14% and 30% [6-8]. Although ETI is a well- established component of a paramedic’s Scope of practice, paramedics have been found to have a higher rate of failed intubation attempts when compared to physicians. One meta-analysis found that the failure rate of non-physician providers was 15 out of 100, while physicians had a failure rate of only one out of 10 [9]. Possible explanations for this dis- parity include differences in initial training, opportunities to perform ETI, and access to additional in-Hospital resources such as neuromuscu- lar block agents [10,11].

Regardless of these differences, every effort should be taken to re- duce ETI failure rates, as significant complications result from delays in definitive airway management. In one study examining in-hospital emergent ETI, patients who required more than two ETI attempts were at a greater risk of developing hypoxemia, regurgitation of gastric contents, bradycardia, and cardiac arrest [12]. These risks may be compounded in the prehospital setting since paramedics often lack the full armamentarium of tools that may be available in the hospital.

The present study examines laryngoscope blade type as a factor of ETI success. This study was conducted over almost nine years in a large suburban-based hospital system. The high volume of patient cases allowed the analysis of 2299 patients with prehospital intuba- tions. The primary finding of our study was that prehospital paramedic intubation using a curved blade had a higher first attempt success rate (86% vs 73%) and overall success rate (96% vs 81%) when compared to a straight blade. The significant differences between success rates of Macintosh versus Miller blades suggest that EMS agencies should per- haps stress the importance of training on the Macintosh blade to better increase familiarity, comfort, and experience resulting in improved first attempt and overall success rates.

A limitation of the study is that individual paramedic-level charac- teristics and success rates were not examined. While all paramedics had the same state-level certification, there could be confounding relat- ing to individual paramedic training, years of clinical experience, and blade preference. As this study was retrospective by design, paramedics had free choice as to which blade to use. Paramedics may not be aware of their strengths and weaknesses regarding use of each blade. Had paramedics decided to use a different blade on the first attempt, success rates may have varied. For example, paramedics may reserve one blade type for intubations they believe will be easier, while employing the other only as a backup. It is therefore possible that the differences in success rates could be attributed to paramedic preference rather than blade performance. A prospective study randomizing paramedics or pa- tients to a specific blade would remove bias, but would be a difficult study to perform given the relative infrequency of intubations on a per-paramedic basis.

Conclusion

This study shows that first attempt and overall intubation success rates of paramedics are higher for Macintosh blades when compared

S.M. Alter et al. / American Journal of Emergency Medicine 36 (2018) 1807–1809 1809

to Miller blades. Although only a small number of patients are intubated in the prehospital setting, it is these patients who are the most critically ill. Therefore, it is important to utilize the most effective method to se- cure the airway. It may also benefit programs training paramedics to in- troduce trainees as early as possible to the Macintosh blade so that familiarity, comfort, and overall experience can be maximized from the very beginning. However, we are not suggesting that those with a strong preference toward the Miller blade should switch to a Macintosh. Individuals who have a strong preference and extensive experience with one blade will likely have a greater rate of success with their pre- ferred choice. Ultimately, the primary goal is to improve patient out- comes, so it is critical that the necessary steps be taken to maximize intubation success rates.

Disclosures

None.

Financial support

None.

Acknowledgements

None.

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